如何将下载按钮直接指向显示图片的网址

Question

我有这个代码。 而且我想当我按下下载图像时，它将在我设计的网页中显示经过过滤的图像。 有人可以帮助我，我该怎么做？

我知道我必须在URL中进行一些更改。 但它不起作用，我真的不知道为什么：

var url = canvas.toDataURL（“ image / png; base64;”）; downloadImage.attr（'href'，url）;

请帮我。

$(function() {

    /*
        In this code, we are going to do the following:

        1. Accept an image on drag and drop
        2. Create a new canvas element (original), with a max size
           of 500x500px (customizable) and keep it in memory
        3. Listen for clicks on the filters. When one is selected:
                3.1 Create a clone of the original canvas
                3.2 Remove any canvas elements currently on the page
                3.3 Append the clone to the #photo div
                3.4 If the selected filter is different from the "Normal"
                    one, call the Caman library. Otherwise do nothing.
                3.5 Mark the selected filter with the "active" class
        4. Trigger the "Normal" filter

    */

    var maxWidth = 500,
        maxHeight = 500,
        photo = $('#photo'),
        originalCanvas = null,
        filters = $('#filters li a'),
        filterContainer = $('#filterContainer');

    // Use the fileReader plugin to listen for
    // file drag and drop on the photo div:

    photo.fileReaderJS({
        on:{
            load: function(e, file){

                // An image has been dropped.

                var img = $('<img>').appendTo(photo),
                    imgWidth, newWidth,
                    imgHeight, newHeight,
                    ratio;

                // Remove canvas elements left on the page
                // from previous image drag/drops.

                photo.find('canvas').remove();
                filters.removeClass('active');

                // When the image is loaded successfully,
                // we can find out its width/height:

                img.load(function() {

                    imgWidth  = this.width;
                    imgHeight = this.height;

                    // Calculate the new image dimensions, so they fit
                    // inside the maxWidth x maxHeight bounding box

                    if (imgWidth >= maxWidth || imgHeight >= maxHeight) {

                        // The image is too large,
                        // resize it to fit a 500x500 square!

                        if (imgWidth > imgHeight) {

                            // Wide
                            ratio = imgWidth / maxWidth;
                            newWidth = maxWidth;
                            newHeight = imgHeight / ratio;

                        } else {

                            // Tall or square
                            ratio = imgHeight / maxHeight;
                            newHeight = maxHeight;
                            newWidth = imgWidth / ratio;

                        }

                    } else {
                        newHeight = imgHeight;
                        newWidth = imgWidth;
                    }

                    // Create the original canvas.

                    originalCanvas = $('<canvas>');
                    var originalContext = originalCanvas[0].getContext('2d');

                    // Set the attributes for centering the canvas

                    originalCanvas.attr({
                        width: newWidth,
                        height: newHeight
                    }).css({
                        marginTop: -newHeight/2,
                        marginLeft: -newWidth/2
                    });

                    // Draw the dropped image to the canvas
                    // with the new dimensions
                    originalContext.drawImage(this, 0, 0, newWidth, newHeight);

                    // We don't need this any more
                    img.remove();

                    filterContainer.fadeIn();

                    // Trigger the default "normal" filter
                    filters.first().click();
                });

                // Set the src of the img, which will
                // trigger the load event when done:

                img.attr('src', e.target.result);
            },

            beforestart: function(file){

                // Accept only images.
                // Returning false will reject the file.

                return /^image/.test(file.type);
            }
        }
    });

    // Listen for clicks on the filters

    filters.click(function(e){

        e.preventDefault();

        var f = $(this);

        if(f.is('.active')){
            // Apply filters only once
            return false;
        }

        filters.removeClass('active');
        f.addClass('active');

        // Clone the canvas
        var clone = originalCanvas.clone();

        // Clone the image stored in the canvas as well
        clone[0].getContext('2d').drawImage(originalCanvas[0],0,0);


        // Add the clone to the page and trigger
        // the Caman library on it

        photo.find('canvas').remove().end().append(clone);

        var effect = $.trim(f[0].id);

        Caman(clone[0], function () {

            // If such an effect exists, use it:

            if( effect in this){
                this[effect]();
                this.render();

                // Show the download button
                showDownload(clone[0]);
            }
            else{
                hideDownload();
            }
        });

    });

    // Use the mousewheel plugin to scroll
    // scroll the div more intuitively

    filterContainer.find('ul').on('mousewheel',function(e, delta){

        this.scrollLeft -= (delta * 50);
        e.preventDefault();

    });

    var downloadImage = $('a.downloadImage');

    function showDownload(canvas){


        downloadImage.off('click').click(function(){

            // When the download link is clicked, get the
            // DataURL of the image and set it as href:

            var url = canvas.toDataURL("image/png;base64;");
            downloadImage.attr('href', url);

        }).fadeIn();

    }

    function hideDownload(){
        downloadImage.fadeOut();
    }

});

Answer 1

您可以尝试以下方法：

var downloadImage = $('a.downloadImage');
var url = canvas.toDataURL("image/png;base64;");
downloadImage.attr('href', url);